Determine the efficiency and feasibility of a new type of power system, the Viscous Rotary Engine Power System (VREPS), using simple analytical models that have been verified through micro-scale fluidic experiments. VREPS will be driven by a Couette-Poiseuille Flow in a small gap between a rotating disk or annulus and a stationary housing, similar to a drum and cylinder viscometer except the fluid is driving the drum in the case of VREPS. The proposed VREPS design, as shown in Figure 1, converts mechanical rotation of the disk or annulus into electrical power by using an integrated switched magnetic pole generator [1]. Three analytical models of the VREPS are developed: a constant property incompressible one-dimensional linearized model, a constant property incompressible two-dimensional model, and a variable property compressible one-dimensional model. These models will be used to compare VREPS performance for a variety of working fluids and conditions. The models are verified using micro particle image velocimetry (ĘPIV) and full three-dimensional numerical analysis using commercially available software. Comparison of the experimental results and the models will reveal the model with the most accurate approximation, which will then be used to design future VREPS devices and thermodynamic cycles involving VREPS devices.